1. Field of the Invention
The present invention relates to a process for uniformly integrating a solid charge, composed of finely divided particles, within a porous substrate.
A particular field of the present invention includes the manufacture of composite materials comprised of a fibrous reinforcement texture densified by a matrix filling at least a part of the texture's pores.
2. Prior Art
One known process for introducing a solid charge within a fibrous texture consists in impregnating the latter using a composition containing a solid charge in the form of finely divided particles in suspension within a liquid carrier.
For instance, document EP-A-0 130 105 discloses a process for manufacturing a ceramic matrix composite material by impregnating the fibrous reinforcement material first with a slurry containing a ceramic powder, and then with a fluid composition based on a precursor which, upon thermal treatment, yields a compound that is identical to the ceramic powder in suspension. The ceramic matrix is consequently formed by both the ceramic powder and the compound derived from the precursor. The use of a ceramic powder suspension in a slurry makes it possible to fill in a large part of the pores in the fibrous reinforcement texture, and thus accelerates its densification compared with the classical process involving successive impregnations with a matrix precursor.
Document FR-A-2 655 977 discloses a similar type of process in which impregnation by a slurry containing a suspension of ceramic powder is achieved by setting up a pressure difference.
There is also known from document FR-A-626 570 a process for the manufacture of a carbon-carbon composite material in which a metallic carbide charge is introduced into the carbon matrix. To this end, the carbon matrix is obtained by impregnating a carbon reinforcement texture with a pitch which is doped with metallic carbide in powder form, and which constitutes a precursor for the carbon matrix.
Among the aforementioned prior art processes, those that employ a slurry containing a powder in suspension for the purpose of densifying the fibrous reinforcement matrix do not allow control of quantity of powder to be integrated into the fibrous texture. Indeed, the latter is generally placed above a filter, while the slurry is admitted from above the fibrous texture, possibly by setting up a pressure difference. The powder contained in the slurry, and retained by the filter, gradually fills in the pores of the fibrous texture. Impregantion is stopped when the powder covers the upper surface of the texture. In this way, the pores are filled in as much as possible by the powder. However, it is not possible to achieve a partial densification by the powder with any degree of uniformity, since the powder accumulates in the parts of the texture lined by the filter.
Similarly, the process in which a carbide charge is incorporated in a pitch that constitutes the carbon matrix precursor does not ensure a uniform distribution of the charge within the resulting matrix.